At least some conventional cellular systems include both public networks (or systems) and private or autonomous networks (or systems). Autonomous networks include private and residential networks, and provide service to users located within a small, generally confined geographical area such as, for example, a house or a building. Public networks provide service to users located within a large geographical area relative to the area serviced by a private network.
Reference is now made to FIG. 7, which shows various blocks 40-46 that represent components (also referred to a "code portions") of a telephone number. Each of the components includes a predetermined number of digits that are each represented by `X`. Block 40 includes a first portion 40a and a second portion 40b. The block 40 represents a telephone number for a telephone, and is hereinafter referred to as a `pre-assigned telephone code`. The first portion 40a specifies an access code for a switching center, such as a Private Branch Exchange (PBX) within an autonomous network or a Message Switching Center within a public network. The second portion 40b represents an extension number for the telephone.
As is known in the art, the pre-assigned telephone code is generally employed in cases where it is desired to place a call from a source telephone located within a public network to a destination telephone located within the public network. Assuming no long distance service is required to place the call, a user of the source telephone may place the call by simply dialing the pre-assigned telephone code for the destination telephone. Typically, the pre-assigned telephone code includes seven digits.
It is known that a user of a source telephone located within an autonomous network can make a telephone call to a user of a destination telephone located within the same network by simply dialing an extension number for the destination telephone. The extension number typically includes four digits (e.g., `4444`), and is represented by the second portion 40b shown in FIG. 7. In some autonomous networks, however, extension numbers for telephones located within the network may include other numbers of digits, such as, by example, five digits (e.g., `5-4444`) or three digits. For example, the combination of blocks 40a' and 40b of FIG. 7 represents a five digit extension number of a telephone located within an autonomous network.
Blocks 44 and 42 of FIG. 7 represent a long distance code and an area code, respectively, of a telephone number. As is known in the art, long distance codes and area codes need to be dialed prior to dialing a pre-assigned telephone code where it is necessary to place a call from a source telephone operating within a region serviced by one area code to a destination telephone operating within a region serviced by another area code. The long distance code 44 typically includes one digit (e.g., `1`) and the area code 42 typically includes three digits (e.g., `203`).
Block 46 of FIG. 7 represents a dialing prefix for an autonomous network, and is hereinafter also referred to as an "extra-network dialing code". In a conventional autonomous network, users of radiotelephones registered with the network typically need to dial a specific extra-network dialing code prior to dialing other portions of a telephone number (e.g., the pre-assigned telephone code, and one or more of the codes 42 and 44), in order to enable a call to be placed to a destination telephone located outside of the autonomous network. By example, assuming that a seven digit pre-assigned telephone code (e.g., `777-1111`) is stored in a memory of a radiotelephone, and that a user operates the radiotelephone so as to retrieve the code from the memory, it is necessary for the user to edit the retrieved code by inserting a specific extra-network dialing code as a dialing prefix (e.g., `8`), before depressing one or more keys (e.g., a `SEND` key) specifying that the call be placed. The extra-network dialing code may include one or more digits.
As can be appreciated, this procedure can be burdensome to the user. Thus, in some cases the user may attempt to avoid this problem by storing the dialing prefix along with the other portions of the telephone number within a memory of the radiotelephone for later retrieval. In this manner, each time the number is subsequently retrieved, it is not necessary to edit the number so as to include the prefix. However, this solution can present another problem in cases where the radiotelephone is registered with a public network, since no dialing prefix is normally required to place calls from radiotelephones registered with public networks. As such, assuming that the telephone number is retrieved from the memory while the radiotelephone is registered with a public network, and that the number includes the dialing prefix, it is necessary for the user to edit the retrieved number so as to remove the prefix from the number before placing the call. Otherwise, the public network will misinterpret the dialing prefix, and the call will not be successfully forwarded.
Another problem can arise in cases where a user is unsure of whether his radiotelephone is registered with the autonomous network or some other network, such as a public network. By example, it is assumed that a user who wishes to place a call to a destination telephone located outside of the autonomous network transports his radiotelephone to an area where, unknowingly to the user, the radiotelephone becomes registered with the public network. It is also assumed that at the time when the user wishes to place the call, the user incorrectly believes that the radiotelephone is registered with the autonomous network, and, as such, unwittingly enters into the radiotelephone a telephone number that includes a dialing prefix. In this case the public network will misinterpret the dialing prefix, resulting in the call not being completed successfully.
As can be appreciated, it would be desirable to provide a radiotelephone that operates in a manner which overcomes the forgoing problems, and which relieves the user of the burden of needing to specify a dialing prefix while placing a call.
Another problem related to the present invention will now be described. As was previously described, it is known that telephone calls can be made between telephones located within an autonomous network using only four or five digit extension numbers (e.g., `4444` or `5-4444`). It is also known that, in order to place a call from a telephone (e.g., a radiotelephone) located outside of an autonomous network to a telephone located within the autonomous network, it is necessary to dial at least a seven digit telephone number (i.e., a pre-assigned telephone code) for the destination telephone. More particularly, assuming that a call is to be placed from a source radiotelephone registered with a public network to a destination telephone located within an autonomous network, and that these networks have a similar area code, it is generally necessary to dial a seven digit telephone number (e.g., `777-1111`) in order to place the call. As another example, and assuming that these networks are located within areas having dissimilar area codes, and that it is necessary to employ a long distance service to complete the call, it is generally necessary to dial an eleven digit number (e.g., `1-203-777-1111`), including an appropriate long distance code, an area code, and the pre-assigned telephone code for the destination telephone, to place the call.
A problem can arise in cases in which a radiotelephone stores one or more telephone numbers for destination telephones. By example, assuming that a memory of radiotelephone stores an extension number for a destination telephone located within the autonomous network, and that a user of the radiotelephone wishes to place a call to the destination telephone while the radiotelephone is registered with a public network, then the user needs retrieve the extension number and then add three or more digits to the extension number in order to enable the call to be placed successfully. Otherwise, the public network will typically not correctly interpret the extension number, and will not forward the call to the destination telephone.
As another example, assuming that the memory stores a telephone number having seven or more digits, and that the user wishes to place a call to a destination telephone corresponding to the stored number while the radiotelephone is registered with the autonomous network, then the user needs to edit the number after retrieval so as to eliminate the non-extension numbers therefrom, in order to enable the call to be placed successfully within the autonomous network. Otherwise, the autonomous network will not correctly interpret the telephone number, and the call will not be completed successfully.
In view of the foregoing description, it can be appreciated that it would be desirable to provide a radiotelephone which overcomes the problems described above.